1. Field of the Invention
The present invention relates to a heat sink in which a channel (water channel) of a cooling fluid is formed by stacking and bonding a plurality of thin plates and to a laser diode obtained by mounting a semiconductor laser device in such a heat sink.
2. Description of the Related Art
In a laser diode of a few W to tens W class, a water cooling system is often employed to realize a higher output and higher reliability. As a heat sink structure for realizing high heat exhaust efficiency, a heat sink of a micro-channel type is well known (refer to, for example, Japanese Unexamined Patent Application Publication No. 2006-294943).
FIG. 8 shows an example of a sectional structure of a laser diode of the related art.
The laser diode is constructed by mounting a semiconductor laser chip 102 on a heat sink 101 having a fine channel structure of a micro-channel type. The heat sink 101 has a structure obtained by stacking and bonding a plurality of thin plates. In the heat sink 101, a water channel 103 (a supply water channel 103A, an intermediate water channel 103B, and an exhaust water channel 103C) through which a cooling fluid passes is formed. In the example of FIG. 8, five thin plates of a first layer 121 as a top layer to a fifth layer 125 are stacked. The first layer 121 is a laser chip mounting plate on which the semiconductor laser chip 102 is mounted. In the second and fourth layers 122 and 124, a radiator fin is formed. In the second to fifth layers 122 to 125, a hole for forming the water channel 103 is formed. The layers are bonded with an insert metal (bonding metal) 105.
A concrete manufacturing procedure of the heat sink 101 having such a structure includes the following steps.    (1) manufacture of base sheets of the layers    (2) etching of sheet materials (formation of a water channel structure)    (3) plating of the sheet materials with an inert metal (bonding metal)    (4) bonding of the sheet materials    (5) heating and pressure-bonding of the sheet materials
As the material of the base sheet, generally, copper (Cu) having high heat conductivity and which is processed easily is used. As the insert metal 105, for example, gold (Au) or silver (Ag) is used. As a bonding method, liquid-phase diffusion bonding, soldering, or the like is used.